The present invention generally relates to an apparatus of a quick coupler for mounting a rotational disk and more particular, relates to an apparatus of a quick connect/disconnect coupler for mounting a rotational disk member equipped with a diamond disk into a pad conditioner disk holder assembly.
Apparatus for polishing thin, flat semi-conductor wafers is well-known in the art. Such apparatus normally includes a polishing head which carries a membrane for engaging and forcing a semiconductor wafer against a wetted polishing surface, such as a polishing pad. Either the pad, or the polishing head is rotated and oscillates the wafer over the polishing surface. The polishing head is forced downwardly onto the polishing surface by a pressurized air system or, similar arrangement. The downward force pressing the polishing head against the polishing surface can be adjusted as desired. The polishing head is typically mounted on an elongated pivoting carrier arm, which can move the pressure head between several operative positions. In one operative position, the carrier arm positions a wafer mounted on the pressure head in contact with the polishing pad. In order to remove the wafer from contact with the polishing surface, the carrier arm is first pivoted upwardly to lift the pressure head and wafer from the polishing surface. The carrier arm is then pivoted laterally to move the pressure head and wafer carried by the pressure head to an auxiliary wafer processing station. The auxiliary processing station may include, for example, a station for cleaning the wafer and/or polishing head, a wafer unload station, or a wafer load station.
More recently, chemical-mechanical polishing (CMP) apparatus has been employed in combination with a pneumatically actuated polishing head. CMP apparatus is used primarily for polishing the front face or device side of a semiconductor wafer during the fabrication of semiconductor devices on the wafer. A wafer is xe2x80x9cplanarizedxe2x80x9d or smoothed one or more times during a fabrication process in order for the top surface of the wafer to be as flat as possible. A wafer is polished by being placed on a carrier and pressed face down onto a polishing pad covered with a slurry of colloidal silica or alumina in de-ionized water.
A schematic of a typical CMP apparatus is shown in FIGS. 1A and 1B. The apparatus 20 for chemical mechanical polishing consists of a rotating wafer holder 14 that holds the wafer 10, the appropriate slurry 24, and a polishing pad 12 which is normally mounted to a rotating table 26 by adhesive means. The polishing pad 12 is applied to the wafer surface 22 at a specific pressure. The chemical mechanical polishing method can be used to provide a planar surface on dielectric layers, on deep and shallow trenches that are filled with polysilicon or oxide, and on various metal films. CMP polishing results from a combination of chemical and mechanical effects. A possible mechanism for the CMP process involves the formation of a chemically altered layer at the surface of the material being polished. The layer is mechanically removed from the underlying bulk material. An altered layer is then regrown on the surface while the process is repeated again. For instance, in metal polishing a metal oxide may be formed and removed repeatedly.
A polishing pad is typically constructed in two layers overlying a platen with the resilient layer as the outer layer of the pad. The layers are typically made of polyurethane and may include a filler for controlling the dimensional stability of the layers. The polishing pad is usually several times the diameter of a wafer and the wafer is kept off-center on the pad to prevent polishing a non-planar surface onto the wafer. The wafer is also rotated to prevent polishing a taper into the wafer. Although the axis of rotation of the wafer and the axis of rotation of the pad are not collinear, the axes must be parallel.
The polishing pad is a consumable item used in a semiconductor wafer fabrication process. Under normal wafer fabrication conditions, the polishing pad is replaced after about 12 hours of usage. Polishing pads may be hard, incompressible pads or soft pads. For oxide polishing, hard and stiffer pads are generally used to achieve planarity. Softer pads are generally used in other polishing processes to achieve improved uniformity and smooth surface. The hard pads and the soft pads may also be combined in an arrangement of stacked pads for customized applications.
A problem frequently encountered in the use of polishing pads in oxide planarization is the rapid deterioration in oxide polishing rates with successive wafers. The cause for the deterioration is known as xe2x80x9cpad glazingxe2x80x9d wherein the surface of a polishing pad becomes smooth such that the pad no longer holds slurry in-between the fibers. This is a physical phenomenon on the pad surface not caused by any chemical reactions between the pad and the slurry.
To remedy the pad glazing effect, numerous techniques of pad conditioning or scrubbing have been proposed to regenerate and restore the pad surface and thereby, restoring the polishing rates of the pad. The pad conditioning techniques include the use of silicon carbide particles, diamond emery paper, blade or knife for scrapping the polishing pad surface. The goal of the conditioning process is to remove polishing debris from the pad surface, re-open the pores, and thus forms micro-scratches in the surface of the pad for improved life time. The pad conditioning process can be carried out either during a polishing process, i.e. known as concurrent conditioning, or after a polishing process.
A conventional conditioning disc for use in pad conditioning is shown in FIG. 1C in a perspective view of a CMP apparatus 50. The apparatus 50 consists of a conditioning head 52 which includes a conditioning disc 68 mounted to a hub frame 70, a polishing pad 56, and a slurry delivery arm 54 positioned over the polishing pad. The conditioning head 52 is mounted on a cover ring 58 which is extended over the top of the polishing pad 56 for making sweeping motion across the entire surface of the pad. The slurry delivery arm 54 is equipped with slurry dispensing nozzles 62 which are used for dispensing a slurry solution on the top surface 60 of the polishing pad 56. Surface grooves 64 are further provided in the top surface 60 to facilitate even distribution of the slurry solution and to help entrapping undesirable particles that are generated by coagulated slurry solution or any other foreign particles which have fallen on top of the polishing pad during a polishing process.
FIG. 2 shows a cross-sectional view of the conditioning head 52 of FIG. 1C. The conditioning head 52 is constructed by a bearing mount 42, a ball-bearing 44, a cylinder rotator 46, and a cylinder shaft 48. The bearing mount 42 and the ball-bearings 44 are mounted stationarily, while the cylinder rotator 46 and the cylinder shaft rotate when driven by a pulley 50. A pneumatic conduit 52 is utilized to supply a pressure onto the cylinder shaft 48 such that a conditioning disk 54 is pushed downwardly onto the surface of a polishing pad to be conditioned. The pneumatic conduit 52 further supplies a negative pressure, i.e. a vacuum onto the cylinder shaft 48, when the conditioning motion of the conditioning disk 54 is to be stopped and that the conditioning disk 54 is to be disengaged from the surface of the polishing pad. An elastomeric diaphragm 56 is used to provide a fluid seal between the cylinder shaft 48 and the cylinder rotator 46 to prevent the back flow of polishing slurry into the pneumatic conduit 52.
In the conventional design of the polishing head shown in FIG. 2, numerous design deficiencies have been discovered which lead to serious processing difficulties. For instance, a one-piece travel housing 30 is mounted inside the cylinder shaft 48 for connecting the conditioning disk 54 to the flat end 32 and for connecting to the drive means, i.e. the pulley 50 through the end 34. When a diamond disk (not shown) mounted to the conditioning disk 54 must be replaced, it is a time consuming and labor intensive task. A technician must first remove a pad conditioner cover (not shown), shift the pad conditioner arm outside the polishing machine, remove the pad conditioner belt, disconnect the pneumatic pipe 52 and then remove a worn diamond disk. Since the conditioning disk 54 can only be dropped to a short distance, i.e. to an engagement position with a polishing pad, there is little space to access the mounting screws for the diamond disk which complicates the disk removal procedure.
It is therefore an object of the present invention to provide an apparatus of a quick coupler for mounting a rotational disk that does not have the drawbacks or shortcoming of the conventional mounting apparatus.
It is another object of the present invention to provide a quick coupler for the quick connect/disconnect of a rotational disk to/from a travel housing when a diamond disk on the rotational disk needs to be replaced.
It is a further object of the present invention to provide a quick coupler for mounting a rotational disk into a pad conditioner disk holder that can be quickly disconnected by disengaging a plurality of jutting keys from a disk holder.
It is another further object of the present invention to provide a quick coupler for mounting a rotational disk that does not require the removal of screws when a diamond disk must be removed from the rotational disk.
It is still another object of the present invention to provide a quick coupler for mounting a rotational disk into a pad conditioner disk holder wherein the rotational disk can be removed by a simple retraction of a retractable ring situated on a travel housing.
It is yet another object of the present invention to provide a pad conditioner disk holder assembly that includes a drive means, a rotational disk, a disk holder and a travel housing.
In accordance with the present invention, a quick coupler for the quick connect/disconnect of a rotational disk into a pad conditioner disk holder is provided.
In a preferred embodiment, a quick coupler for mounting a rotational disk is provided which includes a disk holder of a ring shape having a center aperture formed in a polygon, each side of the polygon is provided with a spring-loaded steel ball and a recessed slot behind each ball adapted for receiving a jutting key situated on and operated by a retractable ring attached to a travel housing, the disk holder is further provided with a planar surface for releasably engaging a rotational disk thereon by mechanical means; and a travel housing of cylindrical shape that has a first end threaded for engaging a drive means and a second end in the polygon shape for intimately engaging the center aperture of the disk holder for transmitting a rotational motion of the drive means, the second end is further provided with a spring-loaded retractable ring for sliding in a longitudinal direction of the travel housing and for operating a plurality of jutting keys attached thereon such that when the second end is pushed into the center aperture of the disk holder, each of the plurality of jutting keys engages one of the steel balls by pushing the balls radially inward in a locked position into a hemispherical recess provided in a flat surface of the polygon-shaped second end of the travel housing.
In the quick coupler for mounting a rotational disk, the center aperture may be formed in a polygon that has at least six sides, or formed in an octagon. The disk holder may further be provided with a recessed slot along an outer peripheral surface of the holder adapted for receiving a retaining ring therein for retaining the steel balls in the holder. The rotational disk may have attached thereon a diamond disk for conditioning a polishing pad. The plurality of jutting keys may be eight jutting keys when the center aperture is formed in an octagon. The mechanical means for engaging the rotational disk to the planar surface of the disk holder may be a plurality of bolts. The drive means may be a pulley and a belt that are connected to a motor driven pulley.
The present invention is further directed to a pad conditioner disk holder assembly that includes a drive means for providing rotational motion to the assembly; a rotational disk for attaching to a disk holder; a disk holder of a ring shape that has a center aperture formed in a polygon, each side of the polygon is provided with a spring-loaded steel ball and a recessed slot behind each ball adapted for receiving a jutting key situated on and operated by a retractable ring attached to a travel housing, the disk holder is further provided with a planar surface for releasably engaging the rotational disk thereon by mechanical means; and a travel housing of cylindrical shape that has a first end threaded for engaging the drive means and a second end in the polygon shape for intimately engaging the center aperture of the disk holder for transmitting a rotational motion of the drive means, the second end is further provided with a spring-loaded retractable ring for sliding in a longitudinal direction of the travel housing and for operating a plurality of jutting keys attached thereon, such that when the second end is pushed into the center aperture of the disk holder each of the plurality of jutting keys engages one of the steel balls by pushing the balls radially inward in a locked position into a hemispherical recess provided in a flat surface of the polygon-shaped second end of the travel housing.
In the pad conditioner disk holder assembly, the drive means may be a pulley and a belt which are connected to a motor driven second pulley. The mechanical means for engaging the rotational disk to the planar surface of the disk holder may be a plurality of screws. The center aperture may be formed in a polygon shape that has at least five sides, or may be formed in a hexagon or octagon. The plurality of jutting keys may be between five and ten jutting keys when the center aperture is formed in a polygon that has between five and ten sides. The rotational disk may have a diamond disk attached thereon for conditioning a polishing pad in a chemical mechanical polishing apparatus.